The concept of treating water with a source of metallic ions to kill bacteria in a body of water is known in the art. A metallic ion such as a silver ion is an effective bactericide for a body of water including recreational water such as swimming pools, spas, jetted tubs or the like and is a preferred material because it is generally easier and safer to use when compared to other known bactericides or algaecides. A further advantage of using silver ion as a bactericide is that silver ion minimizes the need for pH adjustment to the body of water. However, if the concentration of metallic ions such as silver ions in a body of water is too low the ability to kill microorganisms is reduced or lost. Conversely, if the concentration of metallic ions such as silver ions is too high it can potentially lead to undesired effects such as causing the user's skin to turn yellow and staining clothes. Thus when silver ion is used as a disinfectant in a body of water one generally want to maintain the concentration of the silver ion in a range that is effective killing microorganisms without leading to the undesired effects associated with higher levels of silver ions.
Traditionally, the sources of metallic ions used to kill bacteria in recreational water have been limited to metallic ion donors that are readily soluble in the recreational water in order to maintain an effective concentration of the biocides in the body of water. Silver chloride (AgCl), for example, has been a commonly used bactericide for releasing silver ions into the body of water to effectively kill microorganisms. Sodium bromide has also been known to be used with silver chloride to provide an additional and alternative water disinfection system.
One of the problems associated with the use of silver for killing microorganisms is that silver has a tendency to complex with other compounds and become increasingly insoluble thereby reducing the effective microorganisms killing ability of the silver. For example, it would not be anticipated that silver chloride when used in combination with sodium bromide would be an effective prolonged disinfectant system because of the combination's tendency to form insoluble silver bromide crystals, which are not believed to be biologically active in aqueous environments.
The use of Ozone (O3) for water disinfection is also known in the art. Examples of current Ozone uses include treatment of recreational waters and treatment of wastewater. Use of Ozone for water disinfection is generally preferred because it is considered to be an environmentally-friendly biocide that produces no hazardous by-products when used alone. However, Ozone generally cannot be used alone as an effective prolonged bactericide for a body of water including recreational waters such as swimming pools, spas, jetted tubs or the like because Ozone tends to be unstable in water especially at elevated pH, and it is readily volatilized from water.
To overcome the problems associated with the use of Ozone while retaining the benefits of Ozone usage, it is also known in the art to post-treat water that has been treated with Ozone with a more stable biocide. For example, bromine displays excellent biocidal properties even at elevated pH where Ozone is unstable, and is less prone to volatilization from water than Ozone. The use of a source of bromine such as sodium bromide to post-treated water that has gone through the ozonization process is advantageous in that sodium bromide normally requires a strong oxidizer such as ozone in order to transform sodium bromide into the bromine's biocidially active form. The benefit of the dual use of Ozone and a more stable biocide such as bromine is that use of the Ozone requires less amounts of bromine to be used in order to maintain effective levels of water disinfection.
Although the dual use of Ozone and bromide is effective at maintaining an effective level of water disinfection, the problem associated with the dual use of Ozone and bromide is that the bromides contained in the water are partly oxidized by the Ozone to produce bromate, which is highly undesirable in that bromate, in higher concentrations, is a known carcinogenic.
To solve the above problems, it has been discovered that the introduction of small amounts of hydantoins to a body of water that has been treated with Ozone and containing silver ion and bromide ions results in the silver ions forming a complex with the hydantoins and remain soluble to a higher degree thereby retaining the silver's antimicrobial activity compared to the use of silver ion and bromide ions alone. It has also been determined that the hydantoins functions to suppress the oxidization of the bromide by the Ozone to produce bromate.
The present invention includes a device and method for using metal ion donors and bromide ion donors in combination with hydantoins including unhalogenated hydantoins such as 5,5-dimethylhydantoin (hereinafter “DMH”) in a body of water to enhance a concentration of the metal ions in the body of water or to enhance the solubility of metal ions from other metal ion donors to retain the silver's antimicrobial activity in the water while suppressing the oxidization of the bromide by the Ozone to produce bromate.